Field of the Invention
The present invention relates to a radiography system applicable to medical equipment, a nondestructive inspection apparatus and the like, and relates also to an X-ray generating apparatus employed in the radiography system.
Description of the Related Art
A radiography system in which an X-ray generating apparatus is incorporated, irradiates a subject with X-rays from an X-ray generating apparatus, and detects the X-rays penetrating the subject with an X-ray detector. The X-ray generating apparatus used here includes an X-ray generating tube inside an outer case. The X-ray generating tube accelerates electrons emitted from an electron source by a tube voltage, and irradiates a target made of metal, such as tungsten, with the electrons to generate X-rays.
In order to generate desirable X-rays for X-ray radiography by the X-ray generating tube, it is necessary to apply the tube voltage in the range of 40 kV to 150 kV between the electron source and the target and to emit an electron beam of high energy. Therefore, a potential difference of at least several tens of kilovolts is produced between the X-ray generating tube and the outer case. As a means to withstand such a tube voltage, a configuration to fill a space between the X-ray generating tube and the outer case with an insulating member is known. Further, a configuration in which different insulating members are used between an X-ray generating tube and an outer case in an irradiation area and a non-irradiation area of X-ray is described in U.S. Pat. No. 7,949,099.
However, the x-ray generating apparatus described in U.S. Pat. No. 7,949,099 may lack durability because the insulating member of the irradiation area may be degraded and the insulating performance may be lowered when irradiated with radiation.